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Wait to air seal until after blower door test?

I’ve been waiting for cooler weather (in zone 5A) before scheduling an energy audit that includes a blower door test with infrared camera. But now in early fall/late summer is a comfortable time to venture into the attic. Is there any reason to wait until the energy audit to work on obvious air sealing improvements? The only thing that I can really think of is that we might miss out on some potential credits for improvements if our “Before” results limit our improvements.

Our improvement efforts are going to be limited to improving air sealing and then adding attic insulation (blown cellulose, on top of existing skimpy rolled fiberglass batts).

My thinking is that I should do the easy air sealing and start putting in ventilation baffles now, and then use the audit to find the air leaks that I overlooked.

Thanks for your thoughts.

Asked by andrew c
Posted Sep 13, 2017 9:22 AM ET



Some orchardists answer the question, "When is the best time to prune a tree?" this way: "When your tools are sharp."

If you are willing to climb into your attic to seal obvious air leaks, you should definitely do so. The work can be done at any time. (In case you haven't seen it, you might want to read this article: Air Sealing an Attic.)

It's rare for a blower-door operator to be patient enough to spend all day on the job site, depressurizing the house for hours so you can find and seal all the air leaks. Typically, the blower-door operator is anxious to pack up the equipment and move on to the next job.

If you can get the big holes sealed up before the blower-door test starts, you'll be a step ahead. Then, on the day of the blower-door test, you can focus on the small holes that are revealed by depressurization.

Answered by Martin Holladay
Posted Sep 13, 2017 10:02 AM ET


Thanks Martin. Now I just need to decide whether to use caulk or the really messy acoutistical sealant that I already have on hand.

Answered by andrew c
Posted Sep 13, 2017 12:53 PM ET


If you have something messy that needs to be used up, the attic is a better place to make a mess than most other places.

Answered by Charlie Sullivan
Posted Sep 13, 2017 8:28 PM ET


Charlie, good point. One bonus is that batt insulation is really easy to get out of the way so you can caulk or spray foam. Once blown insulation gets put down, everything becomes much harder. Realized that on the last house. I'm still going to put on a cheap "painter's suit" and wear rubber gloves.

Answered by andrew c
Posted Sep 13, 2017 8:44 PM ET


Project feedback

Martin was right – people doing blower door tests are not likely to hang around with their equipment running for hours while you fix air leaks. The company that we used to both air seal and insulate in the attic (plus spray the accessible parts of the rim joist in basement) didn’t really do an audit, they just ran a blower door test to get initial leakage/flow rate, then came back a couple of days after the work was done to get a final number. They did walk around with us with an infrared camera (part of the sales pitch), and at my request he also got out a smoke pencil and poked around near some windows that I was pretty sure were leaking.

However, I’m glad that I waited to do anything other than replace some bathroom vent fans before the attic work, because we are in line to get $700 back from our local utility for the improvements we made, including a 30% (just barely) reduction in air leakage.

I think we made some significant improvements. A few vertical knee walls that had falling down fiberglass batts were spray foamed, 16 (!) can lights were covered w/ mineral wool “top hats”, and all the seams and holes in the framing were sealed. We then added a 6” cap of blown cellulose to bring us up over R50.

One of the things that I verified during the tests is that double hung windows don’t seal as well as casement or awning types that can be pulled tightly closed against their seals. Same goes for sliding doors, and we have two, both of which seal poorly.

Anybody need a mostly full case of really messy acoustical sealant? ☺

Answered by andrew c
Posted Oct 11, 2017 7:51 PM ET


Andrew - if you're serious about offloading the acoustical sealant, I have been collecting materials to build over time and I suspect I'm in relative close proximity to you guessing that your somewhere in SE Michigan?

Answered by Drew Baden
Posted Oct 12, 2017 4:32 AM ET



I'm in R. Hills. Also have some 3M 8067 flashing tape from a different project.

We can talk offline. Contact me thru temporary acct [email protected] dot net if you wish. I'll try to remember to check it in the next day or two.

Answered by andrew c
Posted Oct 12, 2017 9:38 AM ET

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